The present invention is directed to a device for centering and fixing a tool within a support or holder, for example, for locating and fastening a cutting form in a frame-type holder.
In order to cut and crease in one single operation a complete cardboard sheet from manufacturing folded box blanks, the tool used in the cardboard cutting press is made of a rectangular plate which is usually wooden and which has various cutting blades and creasing rules inserted into the plate. This type of tool is generally called a cutting form.
The mounting of a cutting form in the cutting station of a press requires its centering and fixing into a metal frame. There are several methods to achieve the centering and fixing operation for a cutting form into its frame. One can start with the tightening of the cutting form against one of the smaller inner faces of the frame. The tightening is then achieved with a plurality of screws which are positioned along sides of the frame. Of course, the first tightening should not be too strong so that during the second tightening operation on an adjacent side, the cutting form can slightly shift until it touches the inner surface of the other or opposite side of the frame. The centering of the cutting form is thus achieved in two distinctive operations. Moreover, the material used for these cutting forms, which material is usually wood, will deform under the action of the tightening of the screws. To avoid this, one generally uses a dynamometric key or tool for the tightening of the screws which are tightened in a given succession so that the pressure is equally distributed on the whole periphery of the cutting form. This cutting form must be centered with accuracy in the frame so that it can be precisely registered with the coacting cutting and creasing counterparts which face it from another member of the cutting station. The tightening of the cutting form can also be achieved with well known metal tightening wedges or other tightening means. But it is to be noted first that it is difficult with the described system to obtain a pressure which is regularly distributed on the whole periphery of the cutting form and secondly that the measurement of the cutting form suffers from size or shape modifications during this cutting job. The variations are particularly due to hydroscopic conditions, to the raising of the temperature during the processing and to the compression of the wood under the effects of the cutting and tightening pressures.
Consequently, the solution described hereinabove requires a careful control of the tightening and centering of the cutting form and thus a certain amount of time for these operations. Nevertheless, a danger of deforming the frame remains high as the tightening screws tend to apply a bending force on each side of the frame like a beam with several loads placed at several points therealong. No automatic adjustment of the clearance occurs between the cutting form and the frame can be achieved to compensate for size variation of the cutting form. The screws and the tightening wedges will remain as positioned and the form will be able to move in the frame. The consequence of this movement is the lack of accuracy in the registration of the cutting form and its counterpart.